Phoenix  A federal appeals court on Monday refused to lift a stay blocking major parts of Arizona’s immigration law from taking effect and said the federal government is likely to be able to prove the controversial law is unconstitutional.

The 9th U.S. Circuit Court of Appeals turned down an appeal filed by Gov. Jan Brewer. She had asked the appeals court to lift an injunction imposed by a federal judge in Phoenix the day before the law was to take effect on July 29, 2010.

The U.S Justice Department sued to block the law, saying it violates the U.S. Constitution because enforcing immigration law is a federal issue.

U.S. District Court Judge Susan Bolton issued an injunction preventing four major parts of the law from going into effect pending a trial. Monday’s ruling by the three-judge appeals court panel upheld that injunction.

The panel’s opinion said the government is likely to succeed in its arguments that Congress has given the federal government sole authority to enforce immigration laws, and that Arizona’s law violates the Supremacy Clause of the Constitution. One judge dissented.

Brewer’s lawyers said that the federal government hasn’t effectively enforced immigration law and that the state law will assist federal authorities.

“I remain steadfast in my belief that Arizona and other states have a sovereign right and obligation to protect their citizens and enforce immigration law in accordance with federal statute,” Brewer said in a statement.

The governor’s office said Brewer, Arizona Attorney General Tom Horne and their legal team — in conjunction with counsel for the Arizona Legislature — will be considering their legal options, including appealing to a larger 9th Circuit panel or seeking an immediate petition for the U.S. Supreme Court, to lift the injunction.

“SB 1070 is constitutionally sound, and that will be proven when the U.S. Supreme Court takes up this case and makes the proper ruling,” he said.

“We’re obviously pleased with the ruling, but we understand that there could be a long way to go with this litigation,” said Robby Sherwood, a spokesman for the U.S. Attorney for Arizona.

Parts of the law blocked from taking effect while the case works its way through the courts include a provision requiring police to question people’s immigration status while enforcing other laws if there is a reasonable suspicion they’re in the country illegally.

Other provisions that are on hold include: requiring all immigrants to obtain or carry immigration registration papers; making it a state criminal offense for an illegal immigrant to seek work or hold a job; and allowing police to arrest suspected illegal immigrants without a warrant.